In recent years, synthetic polymer waterproofing membrane materials have been introduced to the North American market to replace traditional bituminous asphalt tar/felt paper roofing underlayments in steep slope (>2:12 pitch vs. flat roof) roofing applications. These synthetic materials possess several advantages over the traditional asphalt paper such as greatly improved tensile and tear strength, reduced tendency to tear away from fasteners which delivers greater wind uplift resistance, impervious to water absorption and degradation, engineered to resist UV degradation under prolonged outdoor exposure, lack of any oils leaching out, drying and cracking, and much lower weight per unit area, which facilitates greatly improved handling, storage, and installation productivity.
Although synthetic roofing underlayments possess several significant advantages over traditional asphalt paper, they generally suffer from poor skid resistant properties, most especially under steep slope wet surface conditions. Most underlayments, regardless of their working surface and application pitch, are generally acceptable for use and safe in very dry, non dusty conditions. But as is the nature of roofing, very often the application surface can possess moisture in the form of water, mist, and dew, further referred to as “wet” conditions; in extreme conditions, snow and ice. Depending on the level of surface moisture, and roof pitch, most roofing installers will continue to work (albeit with much greater care and diligence) on the surface of asphalt tar paper, owing to its generally satisfactory performance in minor levels of surface wet conditions.
The greatly reduced coefficient of friction in wet conditions experienced by low skid resistant synthetic roofing underlayments is a significant limiting factor to their enjoying accelerated market penetration in North America as a product class. When this skid resistance factor is combined with their higher cost as compared to commodity asphalt felt paper, this is dual challenge to greater market acceptance. In addition to cost, a roofing applicator will not likely continue to use a product which has such high inherent safety risk issues, both for personal safety, and equally as important, for the securement of various objects temporarily loaded onto the roofing underlayment surface during roof installation (packages of shingles, roofing tiles, etc), which would result in serious safety hazards should they randomly fall from the rooftop surface. For this reason, synthetic polymer, mechanically attached roofing underlayments for the North American market have attempted to mitigate the safety issue by developing improved skid resistant surfaces.
In Europe, however, synthetic underlayments have been used for a longer period of time, are readily accepted, and enjoy a much higher market share in steep slope roofing. The safety issue, although similarly present, isn't as great a concern since the vast majority of steep slope roofing in Europe is done with nailed batten based tile systems, where the roofing applicator has many anchor points to secure to during installation and routine traffic. As well, the type of design used in European homes is different (warm roof) than generally found in North America (cold roof), and this has required the use of moisture breathable roofing membranes, of which engineered synthetics have largely satisfied this need (asphalt paper lacks the sufficient inherent breathability). Thus, an additional driving force is at play higher in Europe which is partly responsible for the enhanced growth and penetration of synthetic polymer underlayments in Europe. Therefore, one finds typically smooth surfaced synthetic roofing underlayments are readily used and accepted as replacements for asphalt paper.
There exist a great many commercially available steep slope roofing underlayments in the global marketplace, comprising both mechanically attached (breathable & non breathable) synthetics, as well as polymer surfaced self adhered bitumen based. All claim some level of skid resistance, but none produce superior or “good” or “excellent” performance as compared to typical asphalt paper under a wide variety of surface loading dynamics found in typical steep slope, wet surface conditions applications. (see Table 1)
TABLE 1Roofing Underlayment Facer/Skid Resistance ComparisonCompanyBrand NameFacer TypeSkid-Resistance1FlexiaTRIFLEX 30 ™Smooth PP* CoatingPoor2RKWRoofTopGuard II ™Nonwoven PPPoorKirschSharksin ™Nonwoven PPPoorPGI/FabreneMATRIX-UL ™Nonwoven PPPoorInterWrapTITANIUM-UDL ™PP NettingFairProctorRoofShield ™Nonwoven PPPoorMFMIce Buster Foil ™Embossed PE** FilmPoorPolyGlassPolyprotector-UDL ™EVA Hot Melt PatternPoorTamkoTile & Metal ™Blistered PE FilmPoorGraceIce&Water Shield ™Hot Melt Adhesive PatternPoorCarlisleWIP 300 ™Polymer Granular FilmPoorCarlisleWIP 100 ™Embossed PE FilmPoorProtectoWrap6RainProof ™Corrugated PE FilmPoorBakorBlueksin ™Polymer Granular FilmPoorDupontTyvek SUPRO ™Embossed HDPEPoorCaplastValmexDivu-Nonwoven PPPoorTopM170 ™DorkenDelta LUXX ™Nonwoven PPPoorDorkenDelta MAXX ™Embossed CoatingPoorKloberPermoForteNonwoven PPPoorSilcartLamintek 18 ™Nonwoven PPPoorVarious30# Asphalt PaperAsphalt/Cellulose FiberGood*PP = Polypropylene Polymer**PE = Polyethyelene Polymer1As tested on a simulated 12:12 (45 degree) inclined wooden deck. Test procedure involves water mist spraying to produce a saturated wet top surface condition, followed by a 60 kg+ weight person wearing rubber soled footwear simulating repeated dynamic incline walking (similar to German Ramp Test DIN 51130 except fixed incline, with handrails, 23 C.)2Ratings: a. Poor: very slippery b. Fair: generally slippery c. Good: intermittently slippery d. Excellent: difficult to induce slippage
A review of the extensive prior art products found in Table 1 clearly indicates the current state of the art is significantly lacking in the availability of a “good” or “excellent” rated, polymer based skid resistant surface for steep slope, wet condition roofing underlayment applications vs. traditional 30# asphalt felt paper.